This invention relates to an improvement in photographic flash device and particularly concerns a photographic flash device capable of eliminating accidental flashing.
In the conventional photographic flash device, a "ready"-indicating glow discharge lamp which indicates completion of charging of the main capacitor is already known. In using such photographic flash device, firstly a power switch is switched on thereby to charge the main capacitor, secondly, after confirming lighting of the "ready"-indicating glow discharge lamp, a triggering circuit is actuated by switching the synchronous switch on thereby to flash a xenon discharge lamp. The power switch of such flash device is kept off when the flashing is not made.
However, even when the power switch of the conventional flash device is off, if the main capacitor has a sufficient charge for a flashing, an inadvertent or accidental switching on of the synchronous switch causes an accidental flashing. In order to avoid such accidental flashing, the assignee hereof has already proposed an improvement of the flash device as disclosed in the U.S. Pat. No. 3,890,538 or in the U.K. Patent specification No. 1,408,710, wherein a safety switch interlocked with a power switch is provided in a triggering circuit of the flash device.
However, the abovementioned improved flash device provided with such interlocked safety switch still has another problem that, if a synchronous switch is inadvertently closed prior to the completion of charging of the main capacitor and the voltage of the main capacitor is above the threshold level for triggering flashing of the xenon-discharge tube, but the voltage is lower than the designed target voltage, then the xenon-discharge tube flashes with a smaller amount of electric charge than designed, thereby emitting smaller intensity of light than designed. Such flashing results in an under-exposure photographing.